1. Field of the Invention
The present invention relates to a wafer processing method of dividing a wafer into a plurality of individual device chips along a plurality of crossing division lines and mounting an adhesive film for die bonding on the back side of each device chip, the plurality of crossing division lines being formed on the front side of the wafer to thereby define a plurality of separate regions where a plurality of devices are respectively formed.
2. Description of the Related Art
In a semiconductor device chip fabrication process, a plurality of crossing division lines are formed on the front side of a substantially disk-shaped semiconductor wafer to thereby define a plurality of separate regions where a plurality of devices such as ICs and LSIs are respectively formed, and these regions are divided from each other along the division lines to thereby produce a plurality of individual semiconductor device chips. As a dividing apparatus for dividing the semiconductor wafer into the individual semiconductor device chips, a dicing saw is generally used. The dicing saw includes a cutting blade having a thickness of about 20 μm to 30 μm for cutting the semiconductor wafer along the division lines. The semiconductor device chips thus obtained are packaged to be widely used in electric equipment such as mobile phones and personal computers.
As a technique of dividing the semiconductor wafer into the individual semiconductor device chips, a so-called dicing before grinding process has been put to practical use. This dicing before grinding process includes the steps of forming a kerf (division groove) having a predetermined depth (corresponding to the finished thickness of each semiconductor device chip) along each division line on the front side of the semiconductor wafer and next grinding the back side of the semiconductor wafer to expose each kerf to the back side of the semiconductor wafer, thereby dividing the semiconductor wafer into the individual semiconductor device chips. By this dicing before grinding process, the thickness of each semiconductor device chip can be reduced to 50 μm or less (see Japanese Patent Laid-open No. 2003-7648, for example).
As another technique of dividing the semiconductor wafer into the individual device chips, a laser processing method called internal processing has also been put to practical use. This laser processing method uses a pulsed laser beam having a transmission wavelength to the wafer, wherein the pulsed laser beam is applied to the wafer in the condition where the focal point of the pulsed laser beam is set inside the wafer in a subject area to be divided. That is, the wafer dividing method using this laser processing method called internal processing includes the steps of applying a pulsed laser beam having a transmission wavelength to the wafer from the back side of the wafer in the condition where the focal point of the pulsed laser beam is set inside the wafer, thereby continuously forming a modified layer inside the wafer along each division line, and next applying an external force to the wafer along each division line where the modified layer is formed to be reduced in strength, thereby breaking the wafer along each division line to obtain the individual device chips (see Japanese Patent No. 3408805, for example).
An adhesive film for die bonding called a die attach film (DAF) having a thickness of 20 μm to 40 μm is mounted on the back side of each semiconductor device chip, and each semiconductor device chip is bonded through the adhesive film to a die bonding frame for supporting the semiconductor device chip by heating. The adhesive film is formed of polyimide resin, epoxy resin, or acrylic resin, for example.
However, in the condition where the adhesive film for die bonding is mounted on the back side of the semiconductor wafer, the back side of the wafer cannot be ground in the dicing before grinding process mentioned above or the laser beam cannot be applied to the wafer from the back side thereof in the laser processing method mentioned above. To solve this problem, there has been proposed a method including the steps of mounting an adhesive film for die bonding on the back side of a semiconductor wafer divided into individual semiconductor device chips, attaching the adhesive film to a dicing tape, and expanding the dicing tape to thereby break the adhesive film along the individual semiconductor device chips (see Japanese Patent Laid-open Nos. 2005-223282 and 2008-235650, for example).